The Reduction of Main Landing Gear Noise

Kennedy, John; Neri, Eleonora; Bennett, Gareth J.

doi:10.2514/6.2016-2900

Cited by 21 publications

(12 citation statements)

References 20 publications

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“…In fact, with respect to aeronautics, typically only the first or second height mode resonance is considered when designing to avoid aeroacoustic cavity noise, such as from burst-disk cavities or vent holes. However, for much larger volumes, such as landing-gear wheel bays or missile bays, higher-order modes have been shown to be excitable within the velocity range of aircraft on approach to landing [49][50][51][52], and as such, deserve to be examined in the literature.…”

Section: A Numerical Analysis: Wave Expansion Methodsmentioning

confidence: 99%

Cavity Resonance Suppression Using Fluidic Spoilers

Bennett¹,

Okolo²,

Zhao³

et al. 2019

AIAA Journal

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This paper examines experimentally the use of a fluidic spoiler to suppress the resonance within a partially closed cylindrical cavity subject to a grazing flow. The relative movement of aircraft and high-speed land-based vehicles through air often results in structural cavities in these vehicles being subject to shear-layer-driven resonance. This can lead to high-amplitude pressure fluctuations within the cavity volume, causing damage to stores or equipment found within landing-gear wheel or weapon bays, for example, or else significant discomfort to the passengers of cars or trains. This large-scale buffeting can also cause vehicle stability problems and can increase drag. This work presents a novel method, in which passive flow control consisting of an upstream fluidic spoiler is used to redirect the upstream flow so that the cavity orifice is shielded. As a result, the grazing flow can no longer detach from the upstream leading edge of the cavity, and thus, vortex shedding is suppressed. The scope of the study includes an examination of higherorder azimuthal acoustic modes excited in the cylindrical cavity: modes which have received little attention in the literature, but which can be readily excited for many flow configurations for partially covered cavities.

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Section: A Numerical Analysis: Wave Expansion Methodsmentioning

confidence: 99%

Cavity Resonance Suppression Using Fluidic Spoilers

Bennett¹,

Okolo²,

Zhao³

et al. 2019

AIAA Journal

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“…To obtain a better understanding of the actual noise emissions of LG systems, wind-tunnel [12,[14][15][16][17] and aircraft flyover experiments [4,9] are typically performed. Whereas the first case offers more controlled flow conditions, it requires the LG model being tested to have a high level of geometric detail to represent the small-scale sound generating mechanisms of the gear [4,5] and it is difficult to replicate the exact conditions present at an aircraft in flight.…”

Section: Introductionmentioning

confidence: 99%

“…The wind-tunnel experiments were performed under the European Clean Sky funded ALLEGRA (Advanced Low Noise Landing (Main and Nose) Gear for Regional Aircraft) project, coordinated by Trinity College Dublin. This project was developed to assess low-noise technologies applied to a full-scale NLG model [15,16] and a half-scale MLG model [17] of a regional aircraft. ALLEGRA consisted of a consortium of universities (Trinity College Dublin and KTH), an aeroacoustic wind-tunnel company (Pininfarina SPA), and European SME manufacturing and design partners (Eurotech and Teknosud) supported by a leading landing gear manufacturer (Magnaghi Aeronautica).…”

Section: Introductionmentioning

confidence: 99%

Comparing flyover noise measurements to full-scale nose landing gear wind tunnel experiments for regional aircraft

Martinez

Neri

Snellen

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

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The noise emissions of the nose landing gear of a full-scale model tested in a wind tunnel, and of three regional aircraft types in flyover measurements are compared in this contribution. The geometries of the nose landing gears in all cases were similar. Microphone arrays and beamforming algorithms were used to determine the sound emissions of the nose landing gears. A good agreement was found between the overall trends of the frequency spectra in all cases. Moreover, the expected 6 th power law with the flow velocity was confirmed for both experiments. On the other hand, strong tonal peaks (at around 2200 Hz) were only found for the flyover tests. As the frequencies of the tones do not depend on the aircraft velocity, they are thought to be caused by cavities found in structural components of the nose landing gear. Removing these tones would cause overall noise reductions up to 2 dB in the frequency range examined. It is, therefore, recommended to further investigate this phenomenon, to include cavity-noise estimations in the current noise prediction models, and to eliminate such cavities where possible.

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“…In practical cases, such as for aircraft take-off and landing where the flow speed varies, it is important to be able to predict these modes so that mitigation measures can be implemented for all modes excited. Recent research published from EU Green Regional Aircraft Clean Sky projects [19][20][21] have demonstrated success in the reduction of nose and main landing gear noise on full and half scale models with the use of low noise technologies. However, the wheel bays continue to be a significant noise source, and for approach and landing, velocities were found to radiate tones at both the Helmholtz resonance frequency of the nose landing gear wheel bay 22 and also at frequencies which were higher than the first, and most typically studied, depth mode for both the nose and main landing gear.…”

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confidence: 99%

Resonant mode characterisation of a cylindrical Helmholtz cavity excited by a shear layer

Bennett

Stephens

Verdugo

2017

The Journal of the Acoustical Society of America

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This paper investigates the interaction between the shear-layer over a circular cavity with a relatively small opening and the flow-excited acoustic response of the volume within to shear-layer instability modes. Within the fluid-resonant category of cavity oscillation, most research has been conducted on rectangular geometries: generally restricted to longitudinal standing waves, or when cylindrical: to Helmholtz resonance. In practical situations, however, where the cavity is subject to a range of flow speeds, many different resonant mode types may be excited. The current work presents a cylindrical cavity design where Helmholtz oscillation, longitudinal resonance, and azimuthal acoustic modes may all be excited upon varying the flow speed. Experiments performed show how lock-on between each of the three fluid-resonances and shear-layer instability modes can be generated. A circumferential array of microphones flush-mounted with the internal surface of the cavity wall was used to decompose the acoustic pressure field into acoustic modes and has verified the excitation of higher order azimuthal modes by the shear-layer. For azimuthal modes especially, the location of the cavity opening affects the pressure response. A numerical solution is validated and provides additional insight and will be applied to more complex aeronautical and automotive geometries in the future.

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The Reduction of Main Landing Gear Noise

Cited by 21 publications

References 20 publications

Cavity Resonance Suppression Using Fluidic Spoilers

Cavity Resonance Suppression Using Fluidic Spoilers

Comparing flyover noise measurements to full-scale nose landing gear wind tunnel experiments for regional aircraft

Resonant mode characterisation of a cylindrical Helmholtz cavity excited by a shear layer

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